Mobile devices capable of using many wireless access protocols are currently entering the marketplace. Phones will soon be available that can access multimedia services, such as streaming video, by either a third generation cellular network or a Wi-Fi network based on the IEEE 802.11 series of standards. FIG. 1 shows this graphically. Mobile device 10 uses the cellular radio network 12 to access a multimedia application 14. Alternatively, mobile device 20 can use another wireless network 22, such as a Wi-Fi network to access the multimedia application 14 via the Internet 24. Typically, these mobile devices are programmed to select the network used based on availability and a preference setting. For example, a multi-protocol phone may be programmed to select a Wi-Fi network when available and the cellular network when no Wi-Fi connection is available.
In a third-generation wireless access network, the radio network is connected to an access gateway, which serves a mobile device. The access gateway performs the mobility agent function to support the network layer mobility of the mobile device. The handoff of the mobile device is typically triggered by the mobility of the mobile device across the serving areas of different access gateways.
In the existing mobile packet data systems, the schemes for a handoff of a mobile device across access gateways have several limitations. These limitations include a lack of preservation of quality of service (QoS) constraints as dictated by an application in the presence of mobility. Particularly with regard to video streaming connections, QoS requires a sufficient available capacity for data transfer to avoid visible interruptions or degradations. The preservation of QoS constraints is required in the case of network layer mobility in the case of intra-access technology mobility as well as in the case of inter-access technology mobility. Intra-access technology mobility is transfer of service from one gateway to another using the same technology, such as a cellular network. Inter-access technology mobility is transfer between technologies, such as switching between cellular technologies and a Wi-Fi domain.
In the case of intra-access technology mobility, the degradation of QoS is likely to occur in cases where the capacity thresholds associated with the serving access gateway are exceeded or if impending fault conditions result in capacity limitations. In the case of inter-access technology mobility, the degradation of QoS is likely to occur in cases, where an appropriate access technology is not selected from among multiple available access technologies. The adverse impact of a degradation of QoS translates into latencies, especially in the case of a VoIP (Voice-over-IP) service and other delay sensitive multimedia services.
In next-generation access networks, multiple wireless access technologies are available for the mobile device for attachment to an access gateway. For a hybrid mobile device, multiple access gateways using a variety of technologies may be available in any particular geographic location. The present invention is directed to the problem of providing seamless transfers between these gateways while maintaining the connection's QoS.